Cryogenic connection for the transmission of high electric power and method of manufacture thereof

ABSTRACT

A cryogenic connection which can be formed directly on the ground on which it is to be laid includes a fluid-tight internal enclosure adapted to carry a cryogenic fluid, a metallic thermal screen surrounding the internal enclosure, a metallic external enclosure surrounding the thermal screen and suspension means for suspending the internal enclosure in the thermal screen and the thermal screen in the external enclosure.

United States Patent Aupoix et al. 51 Oct. 3, 1972 [54] CRYOGENIC CONNECTION FOR THE 3,397,720 8/1968 Jones l74/DlG. 6 TRANSMISSION OF HIGH ELECTRIC 3,431,347 3/1969 Kafka et a1 174/1 5 C POWER AND METHOD OF 3,604,832 9/ 1971 Kohler ..174/DIG. 6 MANUFACTURE THEREOF 3,522,361 7/1970 Kafka ..174/15 C 3 343 035 9/1967 Garwin ..174/15 C [72] Inventors: Marcel Aupoix, Paris; Andre Cuand, GiflsupYvette both of France 3,600,498 8/ 1971 Aupoix et al ..174/15 C [73] Assignees: Compagnie Generale DElectricite; Primary Examiner-Lewis H. Myers LAir Liquide Societe Anonyme Assistant Examiner-A. T. Grimley Pour LEtude et LExploitation Des, AttorneyCraig & Antonelli Paris, France 22 Filed: Sept. 8, 1971 [57] ABSTRACT A cryogenic connection which can be formed directly [21] Appl' NO" 178,614 on the ground on which it is to be laid includes a fluidtight internal enclosure adapted to carry a cryogenic Fol'flgn pp y Data fluid, a metallic thermal screen surrounding the inter- Sept. 8 1970 France ..7032584 enclcsure a metallic external enclosure Surrounding the thermal screen and suspension means for 52 us. c1. ..29/624, 29/455, 29/469, suspending the internal enclosure in the thermal 29/599, 138/113, 174/15 C screen and the thermal screen in the external enclo- [51] Int. Cl. ..H0lb 13/00 Sure- [58] Field of Search.....174/l5 C, 99 B, 28, 29, 16 B, 174/D1G. 6; 29/455, 469, 599, 624

[56] References Cited 4 Claims, 13 Drawing Figures UNITED STATES PATENTS 650,987 6/1900 Ostergren ..l74/DIG. 6

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INVENTORS NARCEL AUPOIK ANDRCULAND QMtaMQQL -6 H122 ATTORNEYS PATENTEBnma 1912 3.6944914 sum 7 or 7 INVENTOR S MARCEL AuPmx IANDRE cuww Craig QMtoMQQQL '9 AITORN E Y5 CRYOGENIC CONNECTION FOR THE TRANSMISSION OF HIGH ELECTRIC POWER AND METHOD OF MANUFACTURE THEREOF The present invention relates to the manufacture of cryogenic connections for the transmission of high electric power.

Cryogenic connections comprise at least one layer formed of a plurality of equidistant conductors which are helically disposed in cylindrical and concentric layers. Each conductor is formed of a tube consisting of electrically conductive material, through which a cryogenic fluid is passed. The external layer is surrounded by a metallic thermal screen which is cooled by means of a cryogenic fluid flowing through ducts in good thermal contact with the screen. This screen is in turn surrounded by a thermal insulator, which is itself surrounded by a fluid-tight enclosure. Means of the enclosure. The internal layer is disposed on a tube and the various layers are electrically insulated, each by a wound-on tape of electrically insulating material.

Such a cryogenic connection gives good results, but difficulties arise in putting it into operation, especially when it is of very large length. Generally speaking, a line for the transmission of electric power by cryogenic connection consists of sections, which are assembled together to reach the desired length of time. Moreover, the various screens or enclosures must have sufficient thickness to resist the mechanical stresses which are exerted on the cryogenic connection when it is being laid and even when it is in position, so that it is very costly.

Another disadvantage of such a cryogenic connection is the multiplication of the operations for its manufacture, to which are added the operations of laying each section, whereby the cost is further increased.

For a very long section of cryogenic connection, the problem then arises in connection with linear expansion, which is appreciable. It is then necessary to take into account these difficulties in the arrangement of the conductors, enclosures and thermal screens, in order that each may expand without causing any deterioration in the structure of the cryogenic connection. There also arises the problem of laying, which necessitates a carefully adapted method of operation.

One of the objects of the present invention is to provide a cryogenic connection which can have a considerable unit length.

The invention concerns notably a method of manu- "facturing a cryogenic connection of great length,

directly on the ground in which it is laid, this cryogenic connection comprising: a fluid-tight metallic internal enclosure adapted to carry a cryogenic fluid, a metallic thermal screen comprising cooling conduits and surrounding the aforesaid internal enclosure without any direct mechanical contact therewith, a metallic external enclosure, separate from the thermal screen, the space between the internal enclosure and the external enclosure being free from gas, a thermal insulator occupying a part of the space between the metallic thermal screen and the external enclosure, an internal suspension system for suspending the internal enclosure in the thermal screen, and an external suspension system for suspending the thermal screen in the external enclosure, the said internal and external enclosures and the said thermal screen each forming a prismatic surface having lateral faces of great length, the said prismatic surfaces which constitute the said internal and external enclosures being sealed in fluid-tight manner, each along one of its longitudinal edges, those portions of the two lateral faces which are situated on either side of the said edge being partially flattened and joined together in fluid-tight manner, and the said thermal screen consisting of a lower portion and an upper portion which are assembled together.

The said method of manufacture is characterized by the fact that it comprises the following stages:

1. A stage for the preformation of the said external enclosure, which comprises:

a bending of a metal strip for preforming the lateral faces of the said external enclosure, the width of this strip being at least equal to the periphery of the said enclosure plus that of the said flattened portions situated on either side of the said edge of the said external enclosure, a partial flattening of the edges of the said strip in such manner as to preform the said flattened portions of the said external enclosure,

2. A stage for the preformation of the said thermal screen, which comprises:

the formation of the said lower portion with an incorporated cooling conduit, the position of the said lower portion in the preformed external enclosure, by means of the said external suspension system,

3. A stage for shaping the said internal enclosure,

which comprises:

a bending of a metal strip for preforming the lateral faces of the said internal enclosure, the length of the said strip being at least equal to the periphery of the said enclosure, plus that of the said flattened portions situated on either side of the said edge of the said internal enclosure, a partial flattening of the edges of the said strip to preform the said flattened portions of the said internal enclosure,

4. A stage comprising:

the closing of the said internal enclosure by bringing together the said edges which have undergone a partial flattening, the fluid-tight coupling of these edges,

5. A stage comprising:

the formation of the said upper portion of the said screen with the provision of the cooling conduits incorporated in this upper portion, the positioning of the said internal enclosure in the said upper portion of the said screen by means of the said internal suspension system,

6. A stage:

for positioning the said upper portion of the said screen and the said internal enclosure on the lower portion of the said screen,

7. A stage comprising:

the positioning of the said thermal insulation between the said screen and the said preformed external enclosure, the fluid-tight closure of the said external enclosure by bringing together and fluid-tight coupling of the said partially flattened edges.

Purely by way of illustration having no limiting character, and for a better understanding of the invention, two examples of the application of the invention will be described with reference to the accompanying drawings wherein:

FIG. 1 is a diagrammatic view in perspective and in section of one embodiment of a cryogenic connection, comprising notably an internal enclosure and an external enclosure,

FIG. 2 is a view in perspective and in section of another embodiment of a cryogenic connection according to the invention, comprising notably an internal enclosure, an external enclosure and a thermal screen.

FIGS. 3 to are sectional views showing the results obtained after the successive stages of the method according to the invention, up to the completion of the cryogenic connection according to FIG. 2,

FIGS. 11a, 11b, and 110 are views in perspective and in section, illustrating the successive stages in the production of the cooling conduits incorporated in the thermal screen.

In accordance with F IG. 1, an internal enclosure 101, which is metallic and fluid-tight, and consists of stainless steel, for example, can carry a cryogenic fluid in a conduit 102 which it forms and within which there are disposed electrical conductors 103. The number of such conductors is limited to three in the figure only by way of example. An external enclosure 104, which is also metallic and fluid-tight and which may be made of steel covered by an anti-corrosion coating, is disposed around the internal enclosure 101, a thermal insulator 105 occupying a part of the space between these two enclosures. This space may also be exhausted in order to ensure a better thermal insulating by appropriate means connected to a branch pipe 11 l.

The thermal insulation 105 may be, for example, an alumina-based superinsulating powder. Each of the enclosures is of prismatic form and of great length, the cross section of each enclosure being of triangular form in the exemplified embodiment.

The prismatic surface formed by each enclosure is sealed along a longitudinal edge of this surface, shown at 116 in the case of the external enclosure and at 117 in the case of the internal enclosure. Two lateral faces are partially flattened (107 and 108 in the case of the external enclosure, and 118 and 119 in the case of the internal enclosure), applied one against the other and fixed by welds, namely spot welds 109 and 114 for ensuring mechanical rigidity and continuous welds 110 and 115 for ensuring fluid-tightness of this enclosure. Grooves 113 and 120 have also been provided to increase the mechanical rigidity. In the figure, the welds 109 and 114 are shown level with the grooves. In a variant, they may be situated elsewhere. Each of the longitudinal faces of each enclosure is formed with regularly spaced indentations such as 112 and 121 in order to improve the mechanical rigidity. The internal enclosure 101 is suspended in the external enclosure 104 by means of suspension cables 106, which may consist, for example, of stainless steel. In the neighborhood of the internal enclosure, the said cable is provided with beads 106' which render possible the displacement of the internal enclosure in the external enclosure when the assembly is cooled. This system is necessary to permit longitudinal expansion of the internal enclosure.

The fluid flowing through the internal enclosure may be, for example, liquid nitrogen in the case of a hyperconducting cryogenic cable.

FIG. 2 is a view in perspective and in section of a cryogenic connection comprising notably an internal enclosure, an external enclosure and a thermal screen.

A fluid-tight metallic internal enclosure 1, for example of stainless steel, can carry a cryogenic fluid in a conduit 2 which it forms and within which there are disposed electric conductors 3. The number of such conductors is limited to three in the figure only by way of example. A metallic thermal screen 4, for example of aluminum, surrounds the said internal enclosure. A fluid-tight metallic external enclosure 5, for example of stainless steel coated with an anti-corrosion agent, surrounds the thermal screen. The thermal insulator 6, which may be, for example, an alumina-based superinsulating powder, partially fills the space between the thermal screen and the enclosure. A vacuum may also be produced between the internal enclosure and the external enclosure by means connected to the branch pipes 17 and 18.

The internal and external enclosures and the screen have a cross section whose envelope is triangular. These enclosures and the screen have the form of a prismatic surface of great length. Each of the enclosures is sealed along a longitudinal edge of the prismatic surface, shown at 11 in the case of the external enclosure and at 12 in the case of the internal enclosure.

Two longitudinal faces on either side of the edge under consideration are partially flattened (13 and 14 in the case of the external enclosure, and 23 and 24 in the case of the internal enclosure), applied one against the other and fixed by means of welds. Spot welds l5 and 25 are provided to ensure mechanical rigidity, and continuous welds 16 and 28 are provided to ensure fluid-tightness of each enclosure. Grooves 26 and 27 are also provided to increase the mechanical rigidity. The thermal screen 4 consists of two parts, a first lower part 29 and a second upper part 19, assembled with the first. The external and internal enclosures are formed with indentations such as 20 and 21 in their longitudinal faces, these indentations being regularly spaced apart so as to improve the mechanical rigidity. The thermal screen 4 comprises incorporated conduits 22 adapted to carry a cryogenic fluid. These conduits may be obtained, for example, by expansion under pressure by a method known as roll bond." Suspension cables 9, which may consist of stainless steel, for example, and beads 10, which may consist of polytetrafluoroethylene, are provided for the suspension of the thermal cable 4 in the external enclosure 5. The same is the case with the suspension of the internal enclosure 1 in the thermal screen 4 by means of the cables 7 and the beads 8. These suspension systems are necessary when the assembly is being cooled and they permit longitudinal expansion of the screen and of the internal enclosure. This cryogenic connection may be superconductive. The cryogenic fluids employed may several hundred meters in length, corresponding to the possibilities of transport of the cables on drums.

By way of purely illustrative and non-limiting example, there will be described an example of the method of manufacturing the cryogenic connection described in the foregoing, with reference to diagrammatic figures.

FIGS. 3 to illustrate the successive stages of the method of manufacturing a cryogenic connection of great length, directly on the ground on which it is laid. Corresponding elements in these figures and in the aforesaid FIG. 2 bear like references.

FIG. 3 diagrammatically illustrates a first stage of the method. A roll of sheet steel of great length, of which the width is equal to the periphery of the external enclosure 5, is unrolled on the ground on which the cryogenic connection is to be laid, so as to form a continuous strip. An appropriate machine traveling along this strip forms the indentations 20, the partially flattened faces 13 and 14 and the stiffening grooves 27 and imparts to the external enclosure its initial form as illustrated in the figure.

FIG. 4 is a diagrammatic view of a second stage of the method. This stage comprises the laying on the ground of a strip, for example of aluminum, whose length is equal to that of the aforesaid strip and whose width is equal to the periphery of the first lower portion of the thermal screen. The appropriate machine travels along this strip and imparts thereto the form of the first lower portion 29 of the thermal screen illustrated in the figure, while the conduit 22 is formed by a method which may be of the roll bond type, which is carried out by expansion under pressure. This method of expansion under pressure will be described in the following with reference to FIG. 1 l.

The cable 9 is positioned with its polytetrafluoroethylene beads 10 and the first lower portion 29 of the thermal screen, which is then laid on these suspension means.

FIG. 5 is a diagrammatic view of a third stage of the method. A stainless steel strip whose width is equal to the periphery of the internal enclosure 1 is unrolled on the ground. With the aid of the appropriate machine, there is imparted thereto a first form as illustrated in the figure, with the additional formation of the indentations 21, of the flattened faces 28 and 24 and of the grooves 26.

FIG. 6 is a diagrammatic view of a fourth stage of the method with conductors 3, in the interior of the said first form of the internal enclosure 1.

FIG. 7 is a diagrammatic view of a fifth stage of the method, comprising the closing of the internal enclosure 1, by bringing together the partially flattened faces 23 and 24, and making the spot welds for the mechanical rigidity and the continuous weld 28 for the fluid-tightness.

FIG. 8 is a diagrammatic view of a sixth stage of the method. There is laid on the ground an aluminum strip whose width is equal to the periphery of the second upper portion 19 of the thermal screen. The conduits 22 are formed, for example by expansion under pressure by a method of the roll bond type, and this second upper portion of the thermal screen is given its final form with the aid of the appropriate machine. The internal enclosure 1 is then attached to the last upper portion 19 of the thermal screen by means of the suspension system comprising the cable 7 and the polytetrafluoroethylene beads 8.

FIG. 9 is a view in perspective of a seventh stage of the method. The internal enclosure suspended from the second upper portion 19 is lowered into the first form of the external enclosure 5, in such a manner that the second upper portion 19 is assembled with the first lower portion 29 of the thermal screen.

FIG. 10 is a diagrammatic view of an eighth stage of the method. The thermal insulation 6 is deposited, the branch pipes 17 and 18 are positioned for the purpose of making the vacuum, and the external enclosure 5 is then closed by bringing together the partially flattened faces 13 and 14 and making the spot welds l5 and the continuous weld 16 for the fluid-tightness. FIGS. 11a, 11b, and 11c diagrammatically illustrate the successive stages of the expansion of a conduit 22 of the thermal screen of FIG. 2. This is an example of the application of the method of the roll bond type.

FIG. 11a is a diagrammatic view in section of a portion of an aluminum strip unrolled on the ground on which the cryogenic connection is to be laid, a cryogenic fluid conduit having to be provided on this portion of the strip. This strip is made, for example, of two aluminum sheets 201 and 202. These two sheets are wleded by rolling. An ink 203 has been deposited on one of the sheets before the rolling. This special ink prevents the welding of the sheets at the place where it is deposited, i.e., in the present instance at the predetermined location of the conduit to be formed.

FIG. 11b illustrates a pre-expansion operation carried out under gas pressure on the unwelded portion 204 of the two sheets. These two sheets move apart slightly as a function of the thickness chosen for the shims 207 and 208, maintained by the plates 205 and 206, subjected to clamping forces represented by the arrows 209 and 210.

FIG. 11c illustrates the final operation of expanding the conduit, so as to give it its final form. Shims 211 and 212 are chosen as a function of the desired height of the conduit, the pressure being higher than in the preceding operation.

It is obvious that it would have been possible to employ different materials for the sheets 102 and 202, and that the conduits could have had a symmetrical form in relation to the welding plane of the two sheets.

This method for the application of a cryogenic connection of great length is is repetitive. An identical section can be added to the preceding one. The sections may be joined by various means ensuring fluidtightness and the mechanical connection and allowing for the longitudinal thermal expansion of the various elements.

It is obvious that a similar method could be applied to the application of a cryogenic connection comprising no thermal screen, and more generally, although the means described have been advantageously chosen for a particular application, that different means producing the same technical effects could be employed without departing from the scope of the invention.

What is claimed is:

1. Method of manufacturing a cryogenic connection of great length, directly on the ground on which it is laid, the cryogenic connection comprising:

a fluid-tight metallic internal enclosure adapted to carry a cryogenic fluid,

a metallic thermal screen comprising cooling conduits and surrounding the aforesaid internal enclosure without any direct mechanical contact therewith,

a metallic external enclosure, separate from the thermal screen, the space between the internal enclosure and the external enclosure being free from gas,

a thermal insulator occupying a part of the space between the metallic thermal screen and the external enclosure,

an internal suspension system for suspending the internal enclosure in the thermal screen, and

an external suspension system for suspending the thermal screen in the external enclosure, the said internal and external enclosures and the said thermal screen each forming a prismatic surface having lateral faces of great length, the said prismatic surfaces which constitute the said internal and external enclosures being sealed in a fluid-tight manner, each along one of its longitudinal edges, those portions of the two lateral faces which are situated on either side of the said edge being partially flattened and joined together in fluid-tight manner, and the said thermal screen consisting of a lower portion and an upper portion which are assembled together, the method of manufacture of said connection comprising the steps of:

preforming the said external enclosure, including bending a metal strip for preforming the lateral faces of the said external enclosure, the width of this strip being at least equal to the periphery of the said enclosure plus that of the said flattened portions situated on either side of the said edge of the said external enclosure, partially flattening the edges of the said strip in such manner as to preform the said flattened portions of the said external enclosure,

preforming the said thermal screen, including forming the said lower portion with an incorporated cooling conduit and positioning of the said lower portion in the preformed external enclosure by means of the said external suspension system, shaping the said internal enclosure, including: bending a metal strip for preforming the lateral faces of the said internal enclosure, the length of the said strip being at least equal to the periphery of the said enclosure plus that of the said flattened portions situated on either side of the said edge of thesaid internal enclosure and partially flattening the edges of the said strip to preform the said flattened portions of the said internal enclosure,

closing the said internal enclosure by bringing together the said edges which have undergone a partial flattening and effecting a fluid-tight coupling of these edges,

forming the said upper portion of the said screen with the provision of the cooling conduits incorporated in this upper portion, positioning the said internal enclosure in the said upper portion of the said screen by means of the said internal suspension system,

positioning the said upper portion of the said screen and the said internal enclosure on the lower portion of the said screen, and u positioning the said thermal insulation between the said screen and the said preformed external enclosure and effecting a fluid-tight closure of the said external enclosure by bringing together and fluidtight coupling of the said partially flattened edges. 2. Method of manufacture according to claim 1, characterized in that it further comprises the step of inserting means for producing vacuum between the said internal and external enclosures.

3. Method according to claim 1, characterized in that it further comprises the step of forming indentations in the lateral faces of the said internal enclosure to increase their rigidity.

4. Method according to claim 1, characterized in that it further comprises the step of forming indentations in the lateral faces of the said external enclosure the increase their rigidity. 

1. Method of manufacturing a cryogenic connection of great length, directly on the ground on which it is laid, the cryogenic connection comprising: a fluid-tight metallic internal enclosure adapted to carry a cryogenic fluid, a metallic thermal screen comprising cooling conduits and surrounding the aforesaid internal enclosure without any direct mechanical contact therewith, a metallic external enclosure, separate from the thermal screen, the space between the internal enclosure and the external enclosure being free from gas, a thermal insulator occupying a part of the space between the metallic thermal screen and the external enclosure, an internal suspension system for suspending the internal enclosure in the thermal screen, and an external suspension system for suspending the thermal screen in the external enclosure, the said internal and external enclosures and the said thermal screen each forming a prismatic surface having lateral faces of great length, the said prismatic surfaces which constitute the said internal and external enclosures being sealed in a fluid-tight manner, each along one of its longitudinal edges, those portions of the two lateral faces which are situated on either side of the said edge being partially flattened and joined together in fluidtight manner, and the said thermal screen consisting of a lower portion and an upper portion which are assembled together, the method of manufacture of said connection comprising the steps of: preforming the said external enclosure, including bending a metal strip for preforming the lateral faces of the said external enclosure, the width of this strip being at least equal to the periphery of the said enclosure plus that of the said flattened portions situated on either side of the said edge of the said external enclosure, partially flattening the edges of the said strip in such manner as to preform the said flattened portions of the said external enclosure, preforming the said thermal screen, including forming the said lower portion with an incorporated cooling conduit and positioning of the said lower portion in the preformed external enclosure by means of the said external suspension system, shaping the said internal enclosure, including: bending a metal strip for preforming the lateral faces of the said internal enclosure, the length of the said strip being at least equal to the periphery of the said enclosure plus that of the said flattened portions situated on either side of the said edge of the said internal enclosure and partially flattening the edges of the said strip to preform the said flattened portions of the said internal enclosure, closing the said internal enclosure by bringing together the said edges which have undergone a partial flattening and effecting a fluid-tight coupling of these edges, forming the said upper portion of the said screen with the provision of the cooling conduits incorporated in this upper portion, positioning the said internal enclosure in the said upper portion of the said screen by means of the said internal suspension system, positioning the said upper portion of the said scReen and the said internal enclosure on the lower portion of the said screen, and positioning the said thermal insulation between the said screen and the said preformed external enclosure and effecting a fluid-tight closure of the said external enclosure by bringing together and fluid-tight coupling of the said partially flattened edges.
 2. Method of manufacture according to claim 1, characterized in that it further comprises the step of inserting means for producing vacuum between the said internal and external enclosures.
 3. Method according to claim 1, characterized in that it further comprises the step of forming indentations in the lateral faces of the said internal enclosure to increase their rigidity.
 4. Method according to claim 1, characterized in that it further comprises the step of forming indentations in the lateral faces of the said external enclosure the increase their rigidity. 